1. Field of the Invention
Embodiments of the present invention relate generally to video systems and, more particularly, to methods and systems for aligning and calibrating videos for video quality measurement.
2. Description of the Related Art
In order to evaluate a video system, it is often necessary to compare videos of the same scene, coming from different sources, different delivery paths, different encoders, different bitrates, etc. This procedure is known as video quality measurement in full-reference mode. For this measurement to yield meaningful results, the two videos must be carefully aligned and calibrated in terms of temporal delay and spatial transformations, before the actual quality assessment can be carried out.
Video alignment and calibration techniques that have been employed in the art compute average temporal and spatial shifts of the frames in the videos being compared and apply those shifts to the entire video during calibration. These techniques cannot handle temporal shifts that vary throughout the video, which are commonly introduced by network losses or buffering issues, and therefore do not always produce accurate results. Other aspects often ignored by conventional methods are possible spatial transformations (e.g., slight stretching or rotation of the video frame) and luminance/color changes (e.g., the test video is brighter than the reference). Finally, carrying out the alignment, calibration, and quality measurement steps in real time is essential for the live evaluation of operational video processing components.